Screw-cutting die



(No Model.)

L. S. SCOTT.

SCREW CUTTING DIE.

No. (563,810. Patented July 14, 1896.

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UNITED STATES PATENT OFFICE.

LAFAYETTE S. SCOTT, 0F SPRINGFIELD, VERMONT.

SCREW-CUTTING DIE.

SPECIFICATION forming part of Letters Patent No. 563,810, dated July 14,1896.

Application lecl May 25, 1895. Serial No. 550,693. (No model.)

To @ZZ whom t may concern:

Be it known that l, LAFAYETTE S. SCOTT, of Springfield, inthe county oflVindsor and State of Vermont, have invented certain new and usefulImprovements in Screw-Cutting Dies, of which the followin g is aspecification.

This invention relates to that class of screwcutting dies in which thecutters or members of the die proper are held in a ring or collet andill the circle of the same.

l-Ieretofore it has been customary to make the cutter or die member in asemicircular form, there being thus two such cutters or members in thedie and each having two cutting sections or faces. The capabilities ofsuch a die in point of adjustment to different diameters are quitelimited, and it is the purpose of my invention to provide a novelconstruction of die which will permit greater-latitude in this respect.

For promoting practical operations of the cutting-sections of a die itis apparent that unnecessary contact of these sections with the workshould be avoided. Only the front edges of the sections and a slightextent of thread back of the same need act on the work, and it istherefore desirable that the remaining portions of the cutting-facesretreat from the work. Now in a semicircular cutter having twocutting-secti ons it is an extremely diflicult matter to provide such aclearance, which should be produced in the hobbing operation. It isapparent that in order to remove more metal at the back edge or heel ofcutting section or face than at the front edge the heel must be advancedtoward the center of the hol), so that the latter in rotating will cutangularly into the face of the blank. Vhere two cutting-faces occur onthe saine piece, as in a semicircular die member, it will be readilyseen that by advancing the heel of one face the whole of the other faceis advanced, and

Vthe hol), while cutting angularly as desired exist under adjustment ofthe die to one diameter, for, considering the die to be adj usted tothat diameter and the semicircular inemloers to then be moved towardeach other to a smaller diameter, it is apparent that the clearance isdiminished, if it does not entirely vanish, for the cutting-faces havenot moved radially toward the center of the work, but more tangentially.

I overcome both ditiiculties above explained by separating the die intofour parts, each having a single cutting-face, and by providingexpanding means at each place of division. It will be seen that inbobbing each of the four sections can have the heel part of its actingface advanced toward the center and suitably backed up, and the hob inrotating will out into each face angularly, so that each face will havethe proper clearance and the proper cutting edge. Morever, with the foursections in the collet of the die they can be adjusted to variousdiameters, while the circumferential clearance is preserved, for the diebeing quartered its sections can be'moved radially and the angularrelation oi' the acting faces to the Work need not vary to anyappreciable extent. In this connection the necessity of expanding meansat each division of the die will be apparent, for the sections shouldall partake of equal extent of movement in adjustment to a certaindiameter of work.

The drawings which accompany and form part of this speciiicationillustrate an embodiment of the invention.

Figure l shows a face View of the complete die. Fig. 2 shows alongitudinal central section of the same. Fig. 3 shows the die proper infront end elevation. Fig. 4 shows the same in side elevation.

The letter a designates the collet of the die, which collet, for thepurposes of adjustment, as will hereinafter appear, is made with atapering bore c', extending part way its length from the front end,where it is oi' smallest diameter. Back of the tapering bore there is aninternally-screw-threaded part a? not partaking of the taper.

The die proper is made up of four quartersections b, together making adie of annular form, and this die has a tapering outer surface b tocorrespond with the tapering bore of the collet. lt will he seen thatthis sec- ICO tional die can be regulated as to diameter by itslongitudinal position in the tapered bore of the collet.

The means for expanding the die to bring its tapering outer surfacesinto intimate contact with the wall of the collet are of the fol lowingdescription: The longitudinal confronting edges of the quarter-sectionsl) are beveled, as shown at b2, the bevel extending throughout thelength of the die. Screws d are entered through holes tapped inthe sidesof the collet, and these screws have conical ends d' to coact with thebeveled edges h2 of the die sections. There are two of these screwsbetween each two die-sections, the two screws of each pair being in alongitudinal line of the die. The opposed bevels form a substantiallyV-sliaped groove whose base is parallel with the axis of the die, andhence the two screws of each pair work uniformly and hold thediesections true.

The die having been brought to the proper position longitudinally of thecollet for a certain diameter of work, the screws d are tight cned sothat their inner conical ends by acting on the beveled confronting edgesof the die-sections expand the die against the wall of the collet. 'Whenthe adjustment of the die is to be changed, it is only necessary toloosen the screws slightly, and then the die can be moved longitudinallyin the collet. Besides expanding the die the screws also serve thepurpose of preventing its turning in the collet. AneXternally-screw-threaded ring c is engaged with the screw-threadedport-ion a2 of the collet and serves to back up the die, said ring beingscrewed up tight against the die when the latter is ready for use.

The dotted lines in Fig. 3 indicate the eirindicate longitudinalclearance, which mayalso be produced in the hobbing operation bybuilding out the inner ends of the die-sections, as will be apparent.

It will be seen that a die of the construction shown possesses thecapabilities explained at the outset of this specification.

Having thus described my invention, what I claim isl. The combination ofa suitably-formed collet; four similar segmental thread-cutting sectionstogether forming an annular die to occupy the collet and each having asingle cutting-face; and means for holding the seetions at differentpositions of radial adjustment to provide for different diameters ofwork, substantially as described.

2. The combination of a collet having a tapering bore, foursimilarsegmental threadcutting sections together forming an annular dielon gitudinally adjustable in the collet and having tapering outersurfaces to fit the tapering bore of the latter and each section havinga single cutting-face; expanding-screws entered between each pair ofconfronting edges of the die-sections whereby each section may partakeof like adjustment. and adjustable means for backing up the die,substantially as described.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 22d day of May, A. D. 1895.

LAFAYETTE SCOTT.

Witnesses:

JEROME lV. PIERCE, F. G. ELLIsoN.

